DEV Community: De

Cats - Meow! 🐱

De — Mon, 21 Mar 2022 17:52:42 +0000

The cat (Felis catus) is a domestic species of a small carnivorous mammal.

And is also a standard Unix utility, yay!

Cat is used to read files sequentially, writing them to standard output.

Open your terminal; use touch to create a file:
$ touch file

$ echo "Hello World" >> file

Prints "Hello world"
$ cat file

Copy the file contents:

$ touch file2

$ cat file >> file2

Prints "Hello world"
$ cat file2

Concatenate multiple files:
$ touch file3

$ cat file file2 >> file3

Block-chained Domains - Handshake & Decentralized web

De — Mon, 21 Mar 2022 16:02:13 +0000

Handshake is a decentralized P2P (peer-to-peer) networking protocol.

Differently from the classic DNS which relies on the IANA database, Handshake uses the block chain to keep an immutable collection of addresses.

Handshake is still in beta but growing rapidly among the internet community.

As of 17 March 2022, Namecheap is the only major domain reseller that lets you buy a handshake domain, with ease.

Domains can be acquired through the auctioning system at hsd-dev.org.

Namebase offers an auctioning platform.

Go get your domain!

Linux V4L - Video Streaming 📹

De — Fri, 18 Mar 2022 13:20:08 +0000

From Wikipedia, Video4Linux (V4L for short) is a collection of device drivers and an API for supporting real-time video capture on Linux systems.

V4L (or it's successor V4L2) are used in many scenarios, such as applying effects to your stream.

Let's Stream

Load the V4L2 module first:

$ modprobe v4l2loopback

The command above will create a virtual video device.
To check the available video devices:

$ v4l2-ctl --list-devices

A "Dummy video device" should be available, for simplicity, we will call this device /dev/video2.

Map the video stream:

$ ffmpeg -re -i VIDEO_NAME.mp4 -map 0:v -f v4l2 /dev/video2

I use VLC to play the video

$ vlc v4l2:///dev/video2

You can also stream from a URL, for example, to stream from an .m3u8 playlist:

$ ffmpeg -i 'https://www.example.com/video/file.m3u8' -c copy -vcodec rawvideo -threads 0 -f v4l2 /dev/video2

The video can now be accessed in real-time from /dev/video2.

Also Youtube-dl can be used to obtain a HLS link to the m3u8 playlist, just use the -g flag

$ youtube-dl -g https://www.youtube.com/watch?v=QquG9a8xpfk

You can use webcamtests.com to see /dev/video2 from your browser.

SSH - A Better VPN 🚀

De — Wed, 16 Mar 2022 19:21:11 +0000

As alternative to VPN, a SOCKS5 tunnel is often a faster, cheaper alternative.

$ ssh USERNAME@IP -D PORT

In the following example, the USERNAME we use is root, the VPS IP is 23.84.52.11 and we want to create a SOCKS5 listening on PORT 2240:

$ ssh root@23.84.52.11 -D 2240

The SOCKS5 proxy should now be available.
Adjust your browser settings accordingly; the proxy host will be 127.0.0.1 or localhost and the port 2240:

127.0.0.1:2240
or
localhost:2240

Finally, if you want to surf without a proxy, Tun2socks is a great tool you can use to tune a SOCKS proxy to a virtual interface.

Internet Everywhere - DNS Tunnel 🚇

De — Wed, 16 Mar 2022 18:50:59 +0000

DNS Tunnel is a great tool for accessing the internet even in the most unlikely places.

At times, you may encounter a faulty internet connection, down for maintenance, filtered by a firewall;
a DNS tunnel can connect you to the internet, and is quite simple to create one.

Pre-requisites

You need a domain name, a VPS and Iodine.

Iodine is the software we will use to tunnel internet data.

Install Iodine

Install Iodine (hyperlink above) in both your server and your personal device, Iodine supports Android, Linux, and Windows.

You may also use a package manager

$ apt install iodine

$ yum install iodine-server

$ pacman -Sy iodine

Set up

Access your domain registrar (eg. Namecheap or Godaddy) DNS dashboard:

Add a DNS record of Type "A", with Name "t1ns" and Data/Value YOUR_VPS_IP

where "YOUR_VPS_IP" is the actual IP of your VPS.

Add a DNS record of Type "NS", with Name "t1" and Data/Value t1ns.YOUR_DOMAIN

where "YOUR_DOMAIN" is the domain you acquired from step 1.
The result should look similar to the image below:

Tunnel data

Make sure the DNS records have propagated:

$ nslookup t1ns.YOUR_DOMAIN

The command above should return your server IP.

$ dig A t1.YOUR_DOMAIN

The command above should confirm the DNS record delegation.

Let's create the tunnel:

Run iodined (note the "d") on your server

$ iodined -f -P My_Super_Password 10.0.0.1 t1.YOUR_DOMAIN

the IP "10.0.0.1" in the command above can be replaced with another free private reserved IP. You may leave it as it is.

Run iodine on your device

$ iodine -f -P My_Super_Password t1.YOUR_DOMAIN

the "-f" option instructs Iodine to run in foreground.

You should be able to reach your server through 10.0.0.1.

Finally, you can establish an SSH SOCKS5 proxy connection to your server, happy surfing.

$ ssh SERVER_USERNAME@10.0.0.1 -D PORT

🐧 Linux - Identify CPU Intensive Processes

De — Wed, 16 Mar 2022 18:46:51 +0000

To list all the current processes, starting from the most CPU intensive

$ top -o %CPU

Once you have identified the process, take not of the PID shown in the leftmost column.

You should see something similar to the image below

In our example, the bash script with PID 1435719 is consuming 100% CPU - out of 1 of 4 cores. (see first entry of the image above)

The command ps displays information about a selection of the active processes.

We can pipe ps to grep to obtain a clear-cut list
of the processes we are looking for.

$ ps aux | grep 1435719

The kill command can be used to stop a process.

kill 1435719